Report 77 24 Computer Assisted Analysis of the High Stanford K S L Resolution Mass Spectra of Antibiotics . Kent Dennis H

The high resolutioa mass spectra of five 12-membered macrolide aglycones related to methynolide were analyzed with the aid of the Meta-DENDRAL subprogram INTSUM. Metastable defocusing data obtained for several prominent ions in the spectra of two of these mpounds support stepwise cleavage processes subsequent to initial ring opening. Their behavior in the mass spectrometer proved to be highly dependent on the substituents present and their location on the macrocyclic ring. A series of empirical mass spectral fragmentation rules, which were derived from these data, proved useful in differentiating between the mass spectra of closely related isomeric structures. These rules were also useful in the analysis of the fragmentation patterns of several 14-and 16-membered macrolide aglycones. I. INTRODUCTION The non-polyene macrolide antibiotics are a class of medically important compounds characterized by a macrocyclic lactone system containing not more than two conjugated double bonds.